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<script>
	//++写在前后的区别
	var a = 3;
	console.log(a++);//3  这条语句执行完了之后 a = 4;
	console.log(++a);//5
	
	var b = 8;
	console.log(4 + b++); //12
	console.log(b); //9

	var c = 4; 
	c++;
	console.log(c); //5

	var f = 15;
	console.log(false + f++ + f + true); 
</script>